1. Field of the Invention
This invention relates in general to submersible well pumps, and in particular to a thrust balancing device for a progressing cavity pump rotated by a submersible pump motor.
2. Description of the Prior Art
Progressing cavity pumps, sometimes called "Moineau" pumps have been used for many years. These types of pumps have a stator and a rotor. The stator is an elastomer formed with an internal bore having a double helical configuration. The rotor has a single helical configuration, and is normally formed of metal. Rotating the rotor causes fluid to be pumped from one end of the stator to the other end.
These pumps have been used to some extent in oil field wells. Normally, the stator will be mounted to the lower end of the tubing, which is lowered into the well. The rotor is lowered on a string of sucker rod and inserted into the stator. The rod is rotated from the surface, normally by an electrical motor. Fluid is drawn in from the annulus in the casing into the lower end of the stator and pumped to the surface through the tubing.
There have been proposals to use a submersible motor to eliminate the need for rods extending to the surface. The motor will be located below the pump for rotating the rotor. One problem with a submersible pump motor system would be that there would be a great deal of thrust on the rotor in deep wells. The thrust is due to the pressure on the output end of the pump. The pressure would create a downward force on the rotor. Large thrust bearings would be needed to absorb the downward thrust. The size of the thrust bearing is necessarily limited by the small diameter of the pump.